Conventionally, in orthodontic treatment, an irregular dental arch is corrected by an orthodontic device moving teeth to appropriate positions, and the orthodontic device has to be removed after treatment. With removal of the device, the dental arch, the width diameter, and occlusion that has been fixed by the device become unstable because they are approaching positions before treatment (the corrected teeth tend to return to an original position).
For this reason, an orthodontic retainer is attached to the dental arch after treatment and, with this orthodontic retainer, in place of the orthodontic device, the teeth subjected to orthodontics are retained at positions after orthodontic treatment (refer to Patent Literature 1).
And, the above-described orthodontic retainer has to be continuously attached for a period until the positions of the teeth subjected to orthodontics become stable.